American boxer Muhammad Ali (1942-2016), nearing the end of his career, told the New York (NY) Times on April 6, 1977:
   
“It’s just a job. Grass grows, birds fly, waves pound the sand. I beat people up.”
 
The quotation has been listed with Ali’s most popular quotes.
 
 
Wikipedia: Muhammad Ali
Muhammad Ali (/ɑːˈliː/; born Cassius Marcellus Clay, Jr., January 17, 1942 – June 3, 2016) was an American professional boxer, generally considered one of the greatest heavyweights in the history of the sport. Early in his career, Ali was known for being a controversial and polarizing figure both inside and outside the boxing ring. He was one of the most recognized sports figures of the past 100 years, crowned “Sportsman of the Century” by Sports Illustrated and “Sports Personality of the Century” by the BBC.
 
6 April 1977, New York (NY) Times, “Life With Ali (in Neutral Corner)” by Joyce Maynard, pg. C1, col. 2:
But he won’t miss boxing, he said, in a somewhat hoarse and weary-sounding voice. “It’s just a job. Grass grows, birds fly, waves pound the sand. I beat people up.”
     
Google Books
Success By Quotes
By Joachim K. Stiller
Lulu Press, Inc. (lulu.com)
2015
Pg. 215:
Muhammad Ali, Boxing
It’s just a job. Grass grows, birds fly, waves pound the sand. I beat people up.
 
BBC
Muhammad Ali - in his own words
4 June 2016 Boxing
(...)
“It’s just a job. Grass grows, birds fly, waves pound the sand. I beat people up.”
 
Twitter
Rahul S Zaware
‏@rahul_zaware
The last one but the best quote from #MohammedAli
“It’s just a job. Grass grows, birds fly, waves pound the sand, I beat people up”
3:14 AM - 4 Jun 2016
Pune, India
   
USA Today
30 of Muhammad Ali’s best quotes
USA TODAY Sports 3:43 a.m. EDT June 4, 2016
(...)
28. “It’s just a job. Grass grows, birds fly, waves pound the sand. I beat people up.”